Internal combustion engine systems may emit certain undesirable air pollutants and particulates as a byproduct of the combustion process. For example, internal combustion engines may produce nitrous oxides (NOx) when combustion within the engine cylinders reaches elevated temperatures. In an effort to control these emissions, engine manufactures have implemented various pollutant-reducing features, such as exhaust gas recirculation (EGR) systems.
An EGR system recirculates a portion of the engine exhaust gas back into the intake side of the engine for combustion with fresh air. By reintroducing the exhaust gas, the EGR system lowers the peak temperatures within the cylinders during combustion, thereby reducing the formation of NOx. However, the amount of NOx emitted may vary based on the flow rate of exhaust in the EGR system (the “EGR flow rate”), among other factors.
As operating parameters of the engine change, the operating parameters of the EGR system must adjust in order to accommodate for varying levels of NOx emissions. Some engine systems adjust for this variability in NOx emissions by controlling the EGR system based only on a calculation of the EGR flow rate. Other engine systems may adjust the EGR system based only on measurements from an NOx sensor. However, each of these EGR adjustment approaches may have limitations over the entire range of engine operation.
One exemplary method of controlling an EGR system can be found in U.S. Patent Application Publication No. 2016/0369723 published to Deb et al. on Dec. 22, 2016 (“the '723 publication”), which discloses a system that regulates exhaust gas recirculation flow rate in an engine to limit NOx emissions. While the method of controlling an EGR system described in the '723 publication may be useful in some applications, it may not provide sufficient control of NOx emissions over the full range of engine operating conditions.
The engine system of the present disclosure may solve one or more of the problems set forth above and/or other problems in the art. The current scope of the disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.